Main Objectives

The objective was to select and adapt mixed microbial cultures (MMCs), able to ferment crude glycerol generated from 2nd generation biodiesel from animal fat, and produce building-blocks and green chemicals, with a special focus on butyric acid; and 2) to establish stable continuous reactor operations with the selected MMCs.

 Main Outcomes

 Different selection and adaptation strategies were tested to obtain MMCs able to convert crude glycerol into preferably butyrate. Different inoculum sources requested different approaches, but showed to be able to acclimatize to the diluted (fat-derived) crude glycerol, without the need of any costly pretreatment (purification) of the feed.

Maximum butyrate production yield was obtained with enriched activated sludge BA_EF, which reached around 0.4 g/g (with 10 g/L substrate).

The inoculum that led to the best butyrate production during steady state in CSTR was obtained through enrichment of anaerobic sludge, grown in MM medium, and was used for subsequent statistical optimization. In general and for all continuous experiments performed with different inocula and media, an HRT of 12h, pH 5.5 and a substrate concentration of 10 g/L (T= 37 °C) allowed to reach a steady state.